Molecular properties of ionic channels underlying action potentials will be studied using a variety of specific chemical and pharmacological agents in voltage clamp experiments on frog fibers and squid giant axon. Small signal current measurements of gating charge movement and conductance fluctuations will be made to study the voltage-sensitive opening and closing of channels. The sodium channel inactivation gating mechanism will be explored using scorpion venom and local anesthetic compounds that artificially induce gating and interact with the normal channel gating mechanisms. Permeant and impermeant ions will be used to locate and characterize energy barriers and binding sites in open channels that govern ion selectivity and the conductance through individual channels. One goal of this research is to obtain a tightly-bound label for the sodium channel. A novel surface electrophoresis technique will be used to alter the distribution and density of acetylcholine receptors and sodium channels to investigate possible aggregation effects on channel function. The metabolic turnover rate of sodium channels in developing an adult muscle fiber will be determined using an irreversible modification of the sodium channel's sensitivity to tetrodotoxin. In addition to furthering our knowledge of neurotoxins, local anesthetics, and other pharmacologically important compounds, this research aims at a better understanding of normal molecular mechanisms in excitable membranes.